cdc.gov/coronavirus

Interim Clinical Considerations for Moderna and Janssen 

COVID-19 Vaccine Booster Doses

Sujan Reddy, MD MSc

October 21, 2021
Outline of Presentation

 Indications for COVID-19 vaccine booster doses

 Heterologous (mix-and-match) booster doses

 COVID-19 vaccine booster administration

 Fully vaccinated definition

 Coadministration with other vaccines

 Contraindications and precautions
Indications for a Booster Dose Following mRNA COVID-19 

Primary Series

 The following recipients of an mRNA primary series should receive a single mRNA COVID-19 vaccine 

booster dose ≥ 6 months after completion of primary series

– ≥65 years 

– ≥18 years and reside in long-term care settings

– Aged 50-64 years with certain underlying medical conditions

 The following recipients of an mRNA primary series may receive a single mRNA COVID-19 vaccine 

booster dose ≥6 months after completion of primary series based on their individual risks and 

benefits

– Aged 18-49 years with certain underlying medical conditions

– Aged 18-64 years at increased risk for SARS-CoV-2 exposure and transmission because of 

occupational or institutional setting

 In general, the same product that was used for the primary regimen should be used for the booster. 
Individual Risk-Benefit Assessment for People who 

“may receive” mRNA Booster Dose

 Individual risk factors for SARS-CoV-2 infection 

– Risk of exposure (occupational and institutional settings)

– Risk for infection (time since completion of primary series)

 Potential impact of SARS-CoV-2 infection

– Risk for severe infection (underlying conditions)

– Risk associated with a person’s circumstances (living with/caring for at-risk individuals or 

consequences of inability to meet obligations due to infection)

 Potential benefits of booster

– Reduced risk of infection, including severe infection

 Potential risks of booster

– Rare risks of serious adverse events (myocarditis, pericarditis, anaphylaxis)

– Common risks of transient local and systemic symptoms
Indications for Booster Dose Following Janssen 

COVID-19 Primary Dose

 People aged ≥18 years who received a single dose Janssen primary series 

should receive a single Janssen COVID-19 booster dose at least 2 months 

after completing their primary series
Heterologous (Mix-and-Match) Booster Dose

 The same product that was used for the primary regimen should be used for the 

booster. 

– If that is not available or another product is preferred, heterologous boosting 

with a single dose of any of the authorized COVID-19 vaccine boosters is 

acceptable

 Heterologous dosing may be considered for the booster dose only.

– All doses of the primary series and additional dose (if indicated for moderately 

to severely immunocompromised people who received 2 doses of mRNA 

vaccine) should utilize the same vaccine product.

 Individual benefit-risk assessment may inform which booster product to use.

– Availability of booster product

– Risk profile of vaccine boosters, including rare events
Additional Considerations for Heterologous 

(Mix-And-Match) Booster Dose

 Interval should follow the interval recommended by the primary series

– People who received a single dose Janssen primary series can receive a mRNA 

COVID-19 booster dose at least 2 months after completing primary series

 If Moderna vaccine booster is used, the booster dose and volume should be utilized 

(50μg in 0.25ml)

– Pfizer-BioNTech and Janssen booster doses are the same dose as primary 

vaccine

– If an individual who is moderately to severely immunocompromised received 

a primary dose of Janssen vaccine and receives a booster dose using Moderna, 

the 50μg dose should be used
Administration of COVID-19 Vaccines

Vaccine Primary series/dose Additional dose in 

immunocompromised +

Booster dose+

Dose

(volume)

N doses 

(interval)

Age

(y)

Dose

(volume)

N doses 

(interval 

sinceprimary 

series)

Age

(y)

Dose

(volume)

N doses 

(interval 

sinceprimary 

series)#

Age

(y)

PfizerBioNTech30 μg

(0.3 ml)

2

(21 d) ≥12 30 μg(0.3 ml)

1

(≥28 d) ≥12 30 μg(0.3 ml)

1

(≥6 m) ≥18§

Moderna 100 μg

(0.5 ml)

2

(28 d) ≥18 100 μg(0.5 ml)

1

(≥28 d) ≥18 50 μg(0.25 ml)

1

(≥6 m) ≥18§

Janssen 5 × 1010 VP

(0.5 ml)

1

(N/A) ≥18 (see booster dose) 5 × 1010 VP(0.5 ml)

1

(≥2 m) ≥18

N = number, y = years, ml = milliliters, m = months, d = days, μg = micrograms, VP= viral particles

+ Moderately to severely immunocompromised people

§ Minimum authorized age group 

#Booster interval based on homologous dosing (booster product is the same as primary series). Heterologous (mix-and-match) booster 

interval is dependent on the recommendation for the primary series
Definition of ‘fully vaccinated’

 For public health purposes, people who have completed a primary vaccine 

series (i.e., 2-dose mRNA vaccine series or a single dose of the Janssen 

vaccine) are considered fully vaccinated ≥2 weeks after completion of the 

primary series

 The above definition applies to all people including those recommended to 

receive an additional single dose due to moderate to severe 

immunocompromise and those recommended to receive a booster dose

 People who have received a booster dose should continue to follow 

guidance for fully vaccinated persons to minimize spread of SARS-CoV-2

https://www.cdc.gov/coronavirus/2019-ncov/vaccines/fully-vaccinated-guidance.html
Coadministration with Other Vaccines

 COVID-19 vaccine booster dose (Pfizer-BioNTech, Moderna, or Janssen) 

may be given with other vaccines, without regard to timing.

 This includes simultaneous administration of COVID-19 vaccines and 

other vaccines on the same day.

 If multiple vaccines are administered at a single visit, administer each 

injection in a different injection site.

https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html#Coadministration 
Contraindications Related to Allergy

 Severe allergic reaction (e.g., anaphylaxis) after a previous dose or to a 

component of the COVID-19 vaccine

 Immediate allergic reaction of any severity to a previous dose or known 

(diagnosed) allergy to a component of the vaccine

 Known polysorbate allergy is a contraindication to Janssen COVID-19 and a 

precaution to mRNA COVID-19 vaccination

– People with a contraindication to the mRNA COVID-19 vaccines 

(including a known allergy to polyethylene glycol [PEG]) have a 

precaution to Janssen COVID-19 vaccine

https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html#Contraindications 
Anaphylaxis

 Anaphylactic reactions 

have been rarely reported 

following receipt of 

COVID-19 vaccines. 

https://www.cdc.gov/vaccines/covid-19/downloads/IntermConsid-Anaphylaxis-covid19-vaccine-sites.pdf
Potential Risks after mRNA Booster Dose: 

Myocarditis and Pericarditis

 Rare risks of myocarditis and pericarditis after receiving an mRNA vaccine

– Based on current data from primary series, the highest risk is observed 

in males aged 12-30 years

 For people who developed myocarditis or pericarditis after mRNA vaccine, 

recommend deferral of COVID-19 booster dose at least until clinical 

syndrome has completely resolved

– Conversations with patient and their clinical team may assist with 

decisions about proceeding with subsequent dose and timing

https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html#underlying-conditions
Potential Risks after Janssen Booster Dose:

Thrombosis with Thrombocytopenia Syndrome (TTS)

 Rare risk of thrombosis with thrombocytopenia syndrome (TTS)

– Based on current data from primary dose, the highest risk is observed in 

women aged 18-49 years 

 For people who developed TTS after Janssen COVID-19 primary vaccine: 

– A booster dose of Janssen vaccine is not recommended

– These individuals may receive a dose of mRNA COVID-19 vaccine as a booster 

at least 2 months following the Janssen dose and after the clinical condition 

has stabilized

– Conversations with patient and their clinical team may assist with decisions 

about the use of mRNA COVID-19 vaccine booster and timing of the booster

https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html#janssen-vaccine-certain-populations
Potential Risks after Janssen Booster Dose:

Guillain-Barré Syndrome

 Rare risk of Guillain-Barré Syndrome (GBS)

 For people who had GBS after Janssen primary vaccine: 

– No data are available on the safety of administering either Janssen or mRNA 

booster dose for this situation

– These individuals should be made aware of the option to receive an mRNA 

COVID-19 vaccine booster at least 2 months after the Janssen dose

– Janssen may still be used as a booster in these individuals, particularly if the 

GBS occurrence was >42 days after vaccination or was assessed as related to a 

non-vaccine factor

– Conversations with patient and their clinical team may assist with decisions 

about administration of the COVID-19 vaccine booster and timing of the 

booster
Acknowledgements

 Mary Chamberland

 Kristine Schmit

 Neela Goswami

 Sarah Mbaeyi

 Kathleen Dooling

 Karen Broder

 Margaret Cortese

 Andrew Kroger

 Rachel Gorwitz

 Erin Tromble
For more information, contact CDC

1-800-CDC-INFO (232-4636)

TTY: 1-888-232-6348 www.cdc.gov

The findings and conclusions in this report are those of the authors and do not necessarily represent the 

official position of the Centers for Disease Control and Prevention.